Casing for a heat-dissipating fan

ABSTRACT

A casing for a heat-dissipating fan defines a space having an air inlet and an air outlet. A bottom plate is provided in the air outlet. The bottom plate rotatably supports a fan wheel having a hub and a plurality of blades extending outward from the hub. An annular wall is formed on the bottom plate and has an outer wall face that tapers gradually toward the bottom plate to form a conic shape.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a casing for a heat-dissipatingfan. In particular, the present invention relates to a casing for aheat-dissipating fan with improved air output and without turbulence.

[0003] 2. Description of the Related Art

[0004]FIG. 1 of the drawings illustrates a conventional heat-dissipatingfan comprising a casing 90 having a bottom plate 91. An axle tube 93 isengaged with an axle seat 92 formed on the bottom plate 91. A statorbobbin 94 is mounted around the axle tube 93. A bearing 95 is mounted inthe axle tube 95 for rotatably holding a shaft 100 of a fan wheel 96.When the fan wheel 96 turns, an air stream is driven to flow from an airinlet 98 toward an air outlet 99. The air stream driven by the blades onthe fan wheel 96 exits the air outlet 99, as illustrated by the longerarrows in FIG. 2. However, a portion of the air stream enters a gapbetween the bottom wall 91 and the stator bobbin 94, as indicated by theshorter arrows in FIG. 2. As a result, turbulence is generated and theamount of air output is decreased in addition to noise generated as aresult of tangential wind.

[0005]FIG. 3 illustrates another conventional heat-dissipating fan, inwhich an annular wall 910 extends upward from the bottom plate 91 toprevent entrance of the air stream into the gap between the bottom plate91 and the stator bobbin 94. However, since the annular wall 910 isperpendicular to the bottom plate 91, a portion of the air stream drivenby the blades as a result of rotation of the fan wheel 96 impedes and isthus reflected by the annular wall 910. As a result, the problems ofturbulence and noise remain unsolved.

SUMMARY OF THE INVENTION

[0006] It is the primary object of the present invention to provide acasing for a heat-dissipating fan, wherein the air stream driven by theblades as a result of rotation of the fan wheel may smoothly exit theair outlet. Thus, the turbulence generated as a result of impingement ofthe air stream on the bottom plate or annular wall is reduced, therebyincreasing the amount of air output.

[0007] A casing for a heat-dissipating fan in accordance with thepresent invention defines a space having an air inlet and an air outlet.A bottom plate is provided in the air outlet. The bottom plate rotatablysupports a fan wheel having a hub and a plurality of blades extendingoutward from the hub. An annular wall is formed on the bottom plate andhas an outer wall face that tapers gradually toward the bottom plate toform a conic shape.

[0008] Other objects, specific advantages, and novel features of theinvention will become more apparent from the following detaileddescription and preferable embodiments when taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a sectional view of a conventional heat-dissipating fan.

[0010]FIG. 2 is an enlarged view of a circled portion of FIG. 1.

[0011]FIG. 3 is a view similar to FIG. 2, illustrating anotherconventional heat-dissipating fan.

[0012]FIG. 4 is a sectional view of a first embodiment of a casing of aheat-dissipating fan in accordance with the present invention.

[0013]FIG. 5 is an enlarged view of a circled portion in FIG. 4.

[0014]FIG. 6 is a view similar to FIG. 5, illustrating a secondembodiment of the casing in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments in accordance with the present inventionwill now be described with reference to the accompanying drawings.

[0016] Referring to FIGS. 4 and 5, a first embodiment of a casing for aheat-dissipating fan in accordance with the present invention generallyincludes a casing 1 defining a space 11 having an air inlet 12 and anair outlet 13. A bottom plate 14 is provided in a central portion of theair outlet 13. An axle seat or axle hole (not labeled) is provided onthe bottom plate 14 for rotatably receiving a shaft (not shown) of a fanwheel 2. The fan wheel 2 includes a plurality of blades 22 extendingradially outward from a hub 21 thereof.

[0017] An annular wall 15 extends upward and outward from the bottomplate 14, forming a conic shape. Namely, the annular wall 15 formed onthe bottom plate 14 has an outer wall face that tapers gradually towardthe bottom plate 14. Preferably, the annular wall 15 includes a top thatis adjacent to but not in contact with a bottom of the hub 21, leaving aminimized gap between the hub 21 and the annular wall 15. The annularwall 15 includes an outer wall face 16 that is at an acute angle θ witha plane on which the bottom plate 14 lies. Preferably, the outer wallface 16 is inclined and the angle θ is 60°-80°. FIG. 6 illustrates asecond embodiment of the invention, wherein the outer wall face 16 ofthe annular wall 15 includes an arcuate portion adjacent to the bottomplate 14. Thus, the air stream driven by the blades 22 as a result ofrotation of the fan wheel 2 is smoothly outputted via the air outlet 13in a maximum amount while avoiding generation of turbulence and noise.

[0018] Preferably, the annular wall 15 has a maximum outer diameter notgreater than a diameter of the hub 21.

[0019] Although the invention has been explained in relation to itspreferred embodiments as mentioned above, it is to be understood thatmany other possible modifications and variations can be made withoutdeparting from the scope of the invention. It is, therefore,contemplated that the appended claims will cover such modifications andvariations that fall within the true scope of the invention.

What is claimed is:
 1. A casing for a heat-dissipating fan, the casingdefining a space having an air inlet and an air outlet, a bottom platebeing provided in the air outlet, the bottom plate being adapted torotatably support a fan wheel having a hub and a plurality of bladesextending outward from the hub, an annular wall being formed on thebottom plate and having an outer wall face that tapers gradually towardthe bottom plate.
 2. The casing for a heat-dissipating fan as claimed inclaim 1, wherein the annular wall is conic.
 3. The casing for aheat-dissipating fan as claimed in claim 1, wherein the annular wallincludes a top that is adjacent to but not in contact with a bottom ofthe hub, leaving a minimized gap between the hub and the annular wall.4. The casing for a heat-dissipating fan as claimed in claim 1, whereinthe outer wall face of the annular wall is at an acute angle of 60°-80°with a plane on which the bottom plate lies.
 5. The casing for aheat-dissipating fan as claimed in claim 1, wherein the outer wall faceof the annular wall is inclined.
 6. The casing for a heat-dissipatingfan as claimed in claim 1, wherein the outer wall face of the annularwall has an arcuate portion adjacent to the bottom plate.
 7. The casingfor a heat-dissipating fan as claimed in claim 1, wherein the annularwall has a maximum outer diameter not greater than a diameter of thehub.